Increased potency of some substituted short peptide analogues in comparison to galanin(1-15)-NH2 in rat fundus strips

The activity of short porcine galanin (Gal) analogues was tested in vitro u sing rat gastric fundus strips. The peptides contracted longitudinal smooth muscle in a concentration-dependent manner with the following order of pot ency: Gal(1-29) >[Cit(14)]Gal(1-15) >[Asp(14)]Gal(1-15) > [Dab(14)]Gal(1-15 )> [Nle(14)] Gal(1-15) >[Dpr(14)]Gal(1-15) > [Arg(14)]Gal(1-15)>[Orn(14)]Ga l(1-15) >Gal(1-15). Only in the case of two peptides, namely [Cit(14)]Gal(1 -15) and [Dab(14)]Gal(1-15) did the values of Hill coefficients, estimated from the appropriate concentration-contraction curves, differ significantly from unity. Our results indicate that both N- and C-terminals of Gal molec ule contribute towards the affinity and activity of Gal in rat gastric smoo th muscle cell receptors, indicating that their integrity is essential for its full excitatory myogenic action. The substitution of histidine with cit ruline, aspartic acid, norleucine or diaminobutyric acid in position 14 of the amino acid chain led to a considerable increase in potency, suggesting that amino acids located at this position might play a crucial role where t he strength of short analogues is concerned. (C) 2001 Academic Press.